This invention relates to a device provided in a fiber processing (spinning preparation) machine, for example, a carding machine, a cleaner or the like for measuring distances between facing surfaces. The machine has a clothed roll which cooperates with a clothed counter element, for example, a clothed flat bar. At least one stationary sensor is provided, by means of which the distance to a clothed surface may be determined.
The distance between the carding cylinder clothing and a facing component is of substantial significance as concerns the carding machine and properties of the fiber. The result of the carding process such as fiber cleaning, nep formation and fiber shortening is largely dependent from the carding gap, that is, the distance between the cylinder clothing and the clothing of the traveling flats or stationary carding elements. The channeling of air about the carding cylinder and heat removal are also dependent from the distance between the cylinder clothing and the clothed or unclothed surfaces, such as mote knife or housing shells. Such clearances are affected by various, partially counteracting factors. A wear of facing clothings leads to an enlargement of the carding gap which, in turn, results in an increase of the nep number and a decrease of the fiber shortening. An increase of the cylinder rpm, for example, for enhancing the cleaning effect, results in an enlargement of the cylinder including its clothing because of the centrifugal forces and thus diminishes the carding gap. Further, when large quantities of fiber or particular types of fiber, for example, chemical fibers are processed, the carding cylinder expands because of the temperature increase, resulting in a decrease of the distances of the cylinder clothing from adjoining components.
The carding clearance is affected particularly by the machine settings, on the one hand, and the condition of the clothing, on the other hand. The most important carding clearance of a card equipped with traveling flats is in the principal carding zone, that is, between the carding cylinder and the traveling flats assembly. Of the two clothings which define the carding clearance at least one is in motion (in most cases both are moving). To increase the output of the card, it has been desirable to select the operating rpm, that is, the operating speed of the movable elements, to be as high as permitted by the fiber processing technology. The working clearance is measured in the radial direction (starting from the rotary axis) of the carding cylinder.
In current carding processes increasingly larger fiber quantities per unit time are being handled, requiring higher speeds of the working components. Alone an increase of the fiber flow rate leads, because of the mechanical work, to an increased heat generation even if the working surface areas remain constant. At the same time, however, the technological carding results (uniformity of sliver, degree of cleaning, reduction of neps, etc.), are increasingly improved which requires larger working surfaces participating in the carding process and a closer setting of the components to the carding cylinder. The share of chemical fibers to be processed continuously increases. As compared to cotton, chemical fibers generate more heat due to their frictional contact with the working components of the fiber processing machine. In contemporary designs the working components of high-performance carding machines are enclosed from all sides in order to comply with the stringent safety requirements, to prevent particle emission into the spinning room and to minimize the maintenance requirements of the machines. Grates or even open, material-guiding surfaces which provide for an air exchange, belong to the past.
In view of the above-listed circumstances, the heat input into the fiber processing machine is significantly increased while the extent of heat removal by means of convection has been substantially reduced. The resulting significant heat-up of the high-performance carding machines leads to increased thermo-elastic deformations which, because of the non-uniform distribution of the temperature field, affect the set distances of the working components: the distances decrease between the carding cylinder and the traveling flat bars, the doffer, the stationary flat bars as well as the discharge locations. In an extreme case the set gap between the working components may completely disappear because of heat-caused expansions, so that relatively moving working components collide with one another. This results in significant damaging of the high-performance carding machine. Particularly the generation of heat in the working zone of the carding machine may lead to unlike thermal expansions between the structural components in case of excessive temperature differences.
In practice the quality of the clothing of the flat bar clothings is visually verified by an attendant at regular intervals; a wear results in an increase of the carding gap. In a known device, as disclosed in European patent document 801,158, a sensor is provided with which the working distance of carding clothings, that is, the carding gap may be measured. What is thus measured is the effective distance of the clothing points of one clothing between that of the facing clothing of the machine element. The machine element may have a clothing or may be formed by a housing shell segment having a guide surface. The sensor is conceived particularly for measuring the working distance between the carding cylinder and the flat bars of a traveling flats assembly where an optical device, positioned laterally, senses the carding clearance between the carding cylinder and the flat bar clothings. It is a disadvantage of such an arrangement that the change of the carding gap cannot lead to a conclusion whether or to what extent such change is caused by the wear of the clothing of the carding cylinder, the clothing of the flat bars or both.